Long-term objectives include a continuation and expansion of investigations of several critical aspects of the reproductive, genetic, populational, behavioral and ecological biology and distribution of the three Ixodes tick species in North America which are known to feed on humans and transmit the spirochete Borrelia burgdorferi, etiological agent of Lyme disease. These investigations will be enlarged by inclusion of reproductive and genetic investigations of I. ricinus and I. persulcatus, the two major European and Asian species which are vectors of B. burgdorferi. Preliminary hybridization experiments among I. scapularis, I. dammini and I. pacificus suggest a potential sterile hybrid genetic control scheme for these species,l and development of this tick control method will be pursued. Finally, tick vector-spirochete relationships will continue to be investigated in the southeastern U.S., particularly Georgia. Specific aim (1) will continue to expand hybridization attempts among I. scapularis, I. dammini and I. pacificus and add I. ricinus and I. persulcatus to the crosses. Specific aim (2) will evaluate the intra- and interspecific genetic variability of each species by chromosomal analysis (including banding), isozyme and morphometric analyses and rDNA probes. Specific aim (3) will test whether the sterile F1 hybrids can be used in a genetic tick control strategy. This will be examined via appropriate backcrosses of hybrids to parent species, mating competitiveness and other appropriate experiments. Specific aim (4) will continue investigations of the quantitative ecology bionomics of I. scapularis. Specific aim (5) will emphasize attempts to determine the natural tick vector(s) of B. burgdorferi in the southeastern U.S. by continuing our survey of suspect ticks and selected vertebrate hosts for presence of B. burgdorferi and vertebrate sera for presence of B. burgdorferi antibodies. Techniques will involve interspecific hybridizations, chromosomal analyses, electrophoretic isozyme analyses, statistical morphometric determinations, rDNA probes, ELISA, fluorescent-antibody (FA) and indirect fluorescent antibody (IFA) techniques using monoclonal antibodies to B. burgdorferi, and spirochete culture (BSK medium).